Mandrel



W. E. BELTZ June 5, 1951 MANDREL Filed Feb. 21, 1946 Fig./

INVENTOR WILLIAM E. BELTZ BY W ATTORNEY Patented June 5, 1951 UNITED STATES PAT NT OFFICE (Granted under the act of March 3, 1883, as amended April 30,- 1928; 370 0. G. 757) 4 Claims.

This invention relates to mandrels and more particularly to a mandrel for use in hardening coil springs.

An object of this invention is to provide a mandrel serving as a mold or form for a spring during heating and cooling of the spring in the course of heat treatment thereof.

Another object of this invention is to provide a mandrel serving as a mold or form for a spring during the heat treatment thereof which will assure even cooling of the spring and prevent warping of it.

In accomplishing these and other objects of the present invention, I have provided improved details of structure, the preferred form of which is illustrated in the accompanying drawing, wherein:

Fig. 1 is a View in elevation showing a mandrel embodying the features of the present invention, said mandrel having a spring in place thereon;

Fig. 2 is a vertical cross-sectional view along a diametral plane of the device of Fig. l; and

Fig. 3 is a perspective detail view of one of the outermembers of the mandrel.

Many springs, after forming, require prolonged heat treatment in order to provide them with the proper characteristics to perform their intended function. This treatment involves heating to a predetermined temperature and cooling at a predetermined rate in such a manner that the spring retains its proper size and shape. It often occurs that the rate of cooling, possibly combined with irregularities in the structure of the spring, causes a distortion of the spring to such an extent that the spring cannot be used in its intended location. The present invention constitutes a mandrel which provides a mold or form that confines a spring to its normal configuration during the heating and coolin process and provides sufiicient mass to provide a relatively slow rate of cooling to the end that the spring returns to normal temperature undistorted.

Referring more particularly to the drawing:

Numeral I (Fig. 2) indicates a hollow cylindrical member, preferably of metal, which may be simply a section of pipe of appropriate length and diameter. To the cylindrical member I at its lower end is attached a flanged ring member 2, having a ring portion 3 and an inwardly extending flange 4. The member 2 may be permanently attached, as by welding at 5 or other suitable means, or may be detachably attached as by screws to the cylinder I. A coil spring 6 to be heat treated slips over the cylinder 1 and its bottom end turn rests against an inner surface 1 of the flange 4. The spring illustrated is generally in the form of a cylindrical helix but departs from a true helix by having its end turns brought into circles. By obvious alterations in design, however, the principles of the present invention may be used on almost any types of springs such as spiral, conical helix, and leaf springs. The spring shown is of circular crosssection but the invention is equally applicable to springs of other cross-section such as rectangular or elliptical. Spaced between the coils of the spring 6 are outer members 8 and 9 of the mandrel, illustrated as two in number and of similar construction.

As shown particularly in Fig. 3 (which is a view of the member 9.), the portions 8 and 9 are generally helical in shape and are so designed as to intertwine with the coils of the spring thereby filling the voids between adjacent spring turns. The space between adjacent turns of each of the outer members, 8 and 9, as shown most clearly at It! in Fig. 3 in the case of member 9, constitutes a slot in which the coil spring rides, engaged along its entire length by the side walls or surfaces II and I2 of the slot. The space between the adjacent surfaces of the two members 8 and 9, such as shown at It and I4, respectively, in Fig. 2, also constitute a slot, forming a continuation of the slot, such as It, in each member. The members 8 and 9 may be made of metal plate cut to the developed generally helical shape and then rolled to cylindrical form or they may be made out of a piece of pipe with the slot cut, milled, or burned in it. Holding the members 8 and 9 in place is a key member I5 cut from rolled plate or pipe to the same cylindrical helix on which the members 8 and 9 are formed. By engagement with end surfaces l6 and ll on members 8 and 9, respectively, the key member l5 serves to wedge the members 8 and 9 into their proper relative position and prevents undesired movement from that position under the action of thermal stresses. A bolt [8 received in a tapped hole (not shown) in the cylinder I fixes the key member l5 to the cylinder I. Raised portions l9 welded or otherwise formed on the members 8 and 9 serve as knobs to facilitate handling and shifting these members.

A removable flanged ring 2!] similar to ring 2 slides over the cylinder l on top of the spring. An inner surface 2| of flange 22 on ring 28 engages the end turn of the spring 6 and restrains it against longitudinal expansion. The outer periphery or surface 23 of the upper end turn of the spring 6 is in contact with ring portion 24 of the flanged ring 20 along inner surface 25. This restrains the spring against radial expansion The ring 20 is prevented from coming off the cylinder by four hand screws 26 received in nuts 21 (Fig. 2) welded to the inside of the cylinder 1.

Operation The members 8 and 9 are threaded into or intertwined with the spring 6 until they are approximately in their proper position to engage the spring along the greater part of its length. This three piece assembly is then slipped over the cylinder I until the bottom turn of the spring rests on the surface I of the flange 4 of the flanged ring 2. The key member [5 is now inserted between the members 8 and 9 thereby forcing them apart into their final position by coaction with their end surfaces l6 and IV. The wedging eifect of the key member l5 may be assisted by pushing on the knobs [9. Bolt i8 is then secured to the cylinder l. The upper flanged ring 20 is now slid over the top of the cylinder I until the inner surface 2| of the flange portion 22 engages the end turn of the spring 6. The hand screws 28 are then screwed into the nuts 21 thus eifectively preventing any upward movement of the ring 2|]. The spring 6 is seen now to be firmly confined against distortion. Longitudinal movement is prevented by the flange p01- tions 4 and 22, while radial expansion is prevented by the ring portions 3 and 2 1. The spring turns are held snugly in a groove, the bottom surface of which is constituted by the external surface of the cylinder l and the side walls of which are constituted by the thickness surfaces of the outer members 8 and 9 and the key member l5. The wire forming each coil is therefore confined on three sides or, in the case of wire of circular cross-section, is confined along three lines of contact with the surfaces of the groove spaced approximately 90 apart around the periphery of the wire.

The mandrel with the spring mounted on it is now ready for heat treatment. The entire assembly is placed in a furnace and heated to the desired temperature for the predetermined length of time and is then removed from the furnace and allowed to cool. The association in contact with the spring of the relatively large mass of metal needed to make up the mandrel causes relatively slower cooling of the spring than in the case where no mandrel is used or where a mandrel with less extensive or less intimate contact with the spring is used. The slow cooling provided by the mass of the mandrel in addition to the restrains imposed by the grooves and end rings of the mandrel combine to prevent warping and distortion of the spring. An example of the proportionate dimensions of the parts to produce the proper cooling is illustrated in the case of a beryllium copper spring of diameter wire in which the inner member of the mandrel was made of pipe 5 /2 in outside diameter and the outer members of the mandrel were made of plate.

It should be noted that the principles of the invention may be embodied in many variations of the illustrated structure. For example, the outer portion of the mandrel shown was made in three sections for convenience, and could not, in this instance, be made in one piece because the spring shown is not a true helix and therefore could not intertwine with a single member. However, in the case of some springs a single outer member may suffice, whereas in other cases 4 a larger number than three may be required because of an intricate design of spring. In all cases, however, the outer members are to be cut to the contour of the spring and are to support the spring along substantially its entire length. Also, if the distance between adjacent turns of a coil spring is great, it may be desirable not to fill the entire void between turns with a large outer mandrel member but to have two or more small mandrel sections spaced longitudinally between the adjacent turns, one engaging each turn, but not necessarily touching each other.

While I have shown but one embodiment of my invention, it is susceptible to modification without departing from the spirit of the invention. I do not wish, therefore, to be limited by the disclosures set forth, but only by the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A mandrel for use in the heat treating of a coil spring, comprising a hollow cylinder having an outside diameter approximately as large as the inside diameter of the spring, a ring surrounding said cylinder at one end thereof having an internally extending flange fixed at said end of said cylinder, the distance between the internal periphery of said ring and the external periphery of said cylinder being approximately equal to the thickness of the material of the coil spring, two generally helical members formed of material approximately as thick as the material of the spring, having an inside diameter to slide over the cylinder, and being of such size and shape as to fit the contour of the spring and to fill the voids between the adjacent turns of the spring extending from the ends of the spring toward its center with the exception of a portion of the void adjacent the central turns, a third member having a generally helical shape constituting a key to fill said portion of the void between the ends of said first two members and to force said first two members into snug engagement with the turns of said spring, means for fastening said key member in place on said cylinder, an internally flanged ring slidable over the other end of said cylinder with the flanged portion of said flanged ring disposed to engage an end of said spring and the ring portion thereof to extend from the flanged portion toward said first mentioned end of said cylinder, the distance between the external periphery of said cylinder and the internal periphery of said ring portion being approximately equal to the thickness of the material of said spring and locking means for preventing the undesired removal of said flanged rin from said cylinder.

2. A mandrel for use in heat treating a coil spring comprising a plurality of generally helical outer plate members shaped for intertwining with the coils of the spring, an inner cylindrical member over which is slidable said spring with said outer members in place, said outer plate members being so shaped and dimensioned as to leave a void between adjacent ends of a pair of said members when intertwined with said spring, a key member shaped and dimensioned to substantially fill said void for insertion between said outer members to assure their proper placement, means for fastening said key member to said inner member, the external surface of said inner member and the radially extending surfaces of said outer members and said key forming a groove engaging and confining the turns of said spring in their normal position along substantially their entire length, and flanged rings on said inner member having portions confining the end turns of said spring against longitudinal distortion and against radial distortion.

3. A mandrel for use in heat treating a coil spring comprising a cylindrical inner member for engaging the inner surface of the turns of the spring substantially along its entire length, a plurality of generally helical outer members shaped for intertwining with the coils of the spring, a pair of end members for engaging the entire end turns of the spring, each of said end members having a first portion for constraining the spring against longitudinal distortion and having a second portion for constraining the spring against radial distortion, and means for preventing undesired displacement of said end members relative to said inner member.

4. A mandrel for use in heat treating a coil spring comprising a cylindrical inner member for engaging the inner surface of the turns of the spring substantially along its entire length, a plurality of generally helical outer members WILLIAM E. BELTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 791,751 Daniels et a1. June 6, 1905 1,731,763 Chancey Oct. 15, 1929 2,356,662 Endsley Aug. 22, 1944 2,410,060 Goodale Oct. 29, 1946 FOREIGN PATENTS Number Country Date 204,986 Great Britain Oct. 11, 1923 

